I feel what this guy's saying about camera makers' goofy workflows. I've done that myself -- gone out and shot a bunch of stuff on my DSLR and let it languish on the SD card for months because importing and editing the photos on my laptop was a bit of a pain.
Honestly though, now that I've plopped down the relatively small amount of money?
The SD-to-Lightning adapter for iOS gets me about 90% of the way there. Sure, I have to physically move the SD card from my DSLR to my phone, but whatever. At that point they get imported and as far as anything in iOS is concerned they're indistinguishable from photos I took with the phone itself.
(I'm reasonably certain this is more or less equally easy to do with Android given an OTG cable or internal SD slot but I don't know)
I'm not even sure I want my camera maker trying to be any smarter than that. Ideally, of course, the phone should be able to put photos onto my camera via wifi or BT. But I can freaking well guarantee that functionality will just rot at some point. It will be broken by some future OS update, or some other reason, and it's not a thing I expect I'd be able to count on in 12 months or 5 years.